CN117795580A - Vehicle control method and vehicle control device - Google Patents

Abstract

In the vehicle control method of the present invention, a controller (16) is caused to execute the following processing: a vehicle speed determination process (S2) for determining whether or not the vehicle speed of the vehicle has fallen below a predetermined speed threshold; a lateral deviation detection process (S10) for detecting a lateral deviation of the vehicle with respect to the lane center or the lane boundary line; a target track generation process (S13) for, when it is determined that the vehicle speed has fallen below the speed threshold, generating a first target travel track of the vehicle so as to suppress a change in lateral deviation after the vehicle speed has fallen below the speed threshold; an avoidance object detection process (S1) for detecting avoidance objects to be avoided by the own vehicle; after the vehicle speed reduction time, the own vehicle is caused to travel along the first target travel path while the deceleration of the own vehicle is adjusted to avoid the avoidance process of the avoidance object (S14).

Description

Vehicle control method and vehicle control device

Technical Field

The present invention relates to a vehicle control method and a vehicle control device.

Background

For example, patent document 1 below describes a travel control device that avoids objects around the host vehicle and causes the host vehicle to travel.

Prior art literature

Patent literature

Patent document 1: international publication No. 2016/024315

Problems to be solved by the invention

However, if a large rudder angle change occurs when automatically avoiding an object, the steering wheel may be greatly moved, and a sense of discomfort may be given to the occupant.

Disclosure of Invention

The purpose of the present invention is to suppress excessive rudder angle changes that occur when automatically avoiding objects.

In the vehicle control method according to an aspect of the present invention, the controller is caused to execute: detecting a vehicle speed reduction time, which is a time when the vehicle speed of the host vehicle has reduced to less than a predetermined speed threshold; detecting a lateral deviation of the host vehicle with respect to the lane center or the lane boundary line; a process of generating a first target travel track of the host vehicle so as to maintain the lateral deviation detected at the time of vehicle speed reduction; detecting an avoidance object to be avoided by the own vehicle; and a process of avoiding the object by adjusting the acceleration/deceleration of the host vehicle while the host vehicle is traveling along the first target travel path after the vehicle speed reduction time.

Effects of the invention

According to the present invention, an excessive rudder angle change occurring when automatically avoiding an object can be suppressed.

Drawings

Fig. 1 is a diagram showing an example of a schematic configuration of a vehicle control device according to an embodiment.

Fig. 2A is an explanatory diagram of a problem of conventional vehicle control.

Fig. 2B is an explanatory diagram of an example of the vehicle control method according to the embodiment.

Fig. 3 is a block diagram showing an example of the functional configuration of the controller in fig. 1.

Fig. 4A is an explanatory diagram showing an example of the target travel track in the case where the speed is not reduced.

Fig. 4B is an explanatory diagram showing an example of the target travel track in the speed reduction state.

Fig. 4C is an explanatory diagram showing an example of the object avoidance control in the speed reduced state.

Fig. 5 is a flowchart of an example of a vehicle control method according to the embodiment.

Fig. 6 is a flowchart of a first example of the speed reduction state detection process.

Fig. 7 is a flowchart of a second example of the speed reduction state detection process.

Fig. 8 is a flowchart of a third example of the speed reduction state detection process.

Detailed Description

(Structure)

Fig. 1 is a diagram showing an example of a schematic configuration of a vehicle in which a vehicle control device according to an embodiment is mounted. The host vehicle 1 includes a vehicle control device 10 that controls the travel of the host vehicle 1. The vehicle control device 10 detects the surrounding running environment of the host vehicle 1 by means of sensors, and assists the running of the host vehicle 1 based on the surrounding running environment. The travel support control of the host vehicle 1 by the vehicle control device 10 may include, for example, autonomous travel control in which the driver does not participate and the host vehicle 1 is automatically caused to travel. The driving support control by the vehicle control device 10 may include driving support control for partially controlling the steering angle, driving force, or braking force of the host vehicle 1 to support the driver of the host vehicle 1.

The vehicle control device 10 includes: an object sensor 11, a vehicle sensor 12, a positioning device 13, a map database (map DB) 14, a navigation device 15, a controller 16, and an actuator 17.

The object sensor 11 includes a plurality of different types of object detection sensors such as a laser radar, a millimeter wave radar, a sonar, a camera, and a LIDAR mounted on the host vehicle 1 to detect objects around the host vehicle 1.

The vehicle sensor 12 detects various information (vehicle signals) obtained from the host vehicle 1. The vehicle sensors 12 include, for example, a vehicle speed sensor, a wheel speed sensor, a 3-axis acceleration sensor, a steering angle sensor that detects a steering angle, a gyro sensor that detects an angular velocity generated in the host vehicle 1, a yaw rate sensor that detects a yaw rate, an accelerator sensor that detects an accelerator opening degree of the host vehicle, and a brake sensor that detects a brake operation amount of the driver.

The positioning device 13 includes a global positioning system receiver, and receives radio waves from a plurality of navigation satellites to measure the current position of the host vehicle 1. The global positioning system receiver may be, for example, an earth positioning system receiver or the like. The positioning device 13 may be, for example, an inertial navigation device.

The map database 14 may store high-precision map data (hereinafter, simply referred to as "high-precision map") suitable as a map for automatic driving. The high-precision map is map data having higher precision than map data for navigation (hereinafter simply referred to as "navigation map") and includes information of lane units more detailed than information of road units. The information of the lane unit includes, for example: information on a lane node indicating a reference point on a lane reference line (for example, a lane center line) and information on a lane link indicating a section form of a lane between the lane nodes. The information of the lane node includes: the identification number of the lane node, the position coordinates, the number of the connected lane links, the identification number of the connected lane links. The information of the lane link includes: the identification number of the lane link, the type of the lane, the width of the lane, the type of the lane boundary line, the shape of the lane dividing line, and the shape of the lane reference line.

The navigation device 15 recognizes the current position of the vehicle by the positioning device 13, and acquires map information of the current position from the map database 14. The navigation device 15 sets a route (hereinafter, sometimes referred to as a "navigation route") up to a road unit where the destination input by the occupant is, and guides the occupant along the route. In addition, the navigation device 15 outputs information of the navigation path to the controller 16. The controller 16 may automatically drive the own vehicle in such a manner as to travel along the navigation path in the autonomous travel control.

The controller 16 is an Electronic Control Unit (ECU) that controls the running of the host vehicle 1. The controller 16 includes peripheral components such as a processor 20 and a memory device 21. The processor 20 may be, for example, a CPU or MPU. The storage device 21 may be provided with a semiconductor storage device, a magnetic storage device, an optical storage device, or the like. The storage device 21 may contain registers, a cache memory, memories such as a ROM and a RAM serving as a main storage device. The functions of the controller 16 described below are realized, for example, by the processor 20 executing a computer program stored in the storage device 21. The controller 16 may be formed of dedicated hardware (e.g., a programmable logic device of an FPGA) for performing various information processing described below.

The actuator 17 operates the steering wheel, the accelerator opening degree, and the brake device of the own vehicle 1 in accordance with a control signal from the controller 16 to generate vehicle behavior of the own vehicle 1. The actuator 17 includes: a steering actuator that controls a steering angle of a steering of the vehicle 1, an accelerator opening actuator that controls an accelerator opening of the vehicle 1, and a brake control actuator that controls a braking operation of a brake device.

Next, an example of control of the host vehicle 1 by the controller 16 will be described. Fig. 2A is an explanatory diagram of a conventional vehicle control problem.

Now, assume that a control is performed to set a target travel path of the host vehicle 1 along the lane center 2c of the lane 2, and to cause the host vehicle 1 to travel along the target travel path and stop at the target stop position P1. The target stop position P1 may be a position immediately before a predetermined distance of the preceding vehicle 3 or a stop line, not shown, for example. On the lane 2 in front of the host vehicle 1, there are parked vehicles 4a and 4b as avoidance objects to be avoided by the host vehicle 1. Therefore, the host vehicle 1 is driven so as to approach the target driving locus along the lane center 2c while maintaining the distance from the parked vehicles 4a and 4b. For example, the host vehicle 1 travels along the trajectory T.

In the example of the trajectory T, the vehicle travels with a deviation (hereinafter, sometimes referred to as a "lateral deviation") in the lane width direction from the lane center 2c (i.e., the target travel trajectory) as indicated by an arrow 5a in order to maintain the distance from the parked vehicle 4 a. After passing through the parked vehicle 4a, steering is performed to the left as indicated by arrow 5b to eliminate the lateral deviation. In order to maintain the distance from the parked vehicle 4b in front of the target stop position P1, the vehicle is steered to the left as indicated by an arrow 5c, and a lateral deviation from the target travel path occurs. After passing through the parked vehicle 4b, steering is performed to the right as indicated by an arrow 5d to eliminate the lateral deviation.

In this way, when steering is performed to eliminate lateral deviation after passing through the parked vehicle 4b, there is a possibility that steering angle variation becomes large. For example, when the host vehicle 1 is stopped at the target stop position P1, the vehicle speed of the host vehicle 1 is extremely low (for example, less than 2.0 m/s). At such extremely low speeds, steering angle changes required to eliminate lateral deviation may become large. This is because, at extremely low speeds where the lateral speed is small, the turning curvature radius becomes small. As a result, the steering wheel may be greatly moved, which may cause discomfort to the occupant.

Fig. 2B is an explanatory diagram of an example of the vehicle control method according to the embodiment. In the vehicle control method of the present embodiment, it is determined whether or not the vehicle speed of the host vehicle 1 has fallen below a predetermined speed threshold. Further, the lateral deviation Yoff of the host vehicle 1 with respect to the lane center 2c is detected. The lateral deviation Yoff of the host vehicle 1 with respect to the lane boundary line of the lane 2 may also be detected. When it is determined that the vehicle speed has fallen below the speed threshold, the target travel locus X of the vehicle is generated so as to suppress a change in the lateral deviation Yoff after the vehicle speed reduction time T1, which is the time at which the vehicle speed has fallen below the speed threshold.

For example, the vehicle speed reduction time T1 may be detected or estimated, and the lateral deviation Yoff of the host vehicle 1 with respect to the lane center 2c or the lane boundary line at the vehicle speed reduction time T1 may be detected. Then, the target running track X of the host vehicle may be generated so as to maintain the lateral deviation Yoff detected at the vehicle speed reduction time T1.

When an avoidance target object (in the example of fig. 2B, the parked vehicle 4B) to be avoided by the host vehicle 1 is detected, the avoidance target object is avoided by adjusting the deceleration of the host vehicle 1 while traveling along the target travel locus X after the vehicle speed reduction time T1.

Therefore, during a period after the vehicle speed reduction time T1, lateral movement for avoiding the avoidance object (the parked vehicle 4B in the example of fig. 2B) is suppressed. Therefore, the change in rudder angle for avoiding the avoidance object in the state where the speed of the host vehicle is low can be suppressed. As a result, the rotation of the steering wheel can be suppressed.

When the avoidance target object (for example, the parked vehicle 4 a) is avoided at a time before the vehicle speed reduction time T1, the target travel locus X is set so as to maintain the lateral deviation Yoff at the vehicle speed reduction time T1. Therefore, since there is no operation to return to the lateral position in the lane before the avoidance behavior, it is possible to suppress the rudder angle change in the state where the speed of the vehicle is low. As a result, the rotation of the steering wheel can be suppressed.

The function of the controller 16 is described in detail below. Fig. 3 is a block diagram showing an example of the functional configuration of the controller 16. The controller 16 includes: an object detection unit 30, a vehicle position estimation unit 31, a map acquisition unit 32, a detection integration unit 33, an object tracking unit 34, an intra-map position calculation unit 35, and a vehicle control unit 36.

The object detection unit 30 detects the position, posture, size, speed, and the like of an object around the host vehicle 1, for example, a vehicle (automobile or motorcycle), a pedestrian, an obstacle, and the like, based on the detection signal of the object sensor 11. The object detection unit 30 outputs a detection result indicating a two-dimensional position, posture, size, speed, and the like of the object in a zenith view (also referred to as a plan view) in which the vehicle 1 is viewed from the air, for example.

The vehicle position estimating unit 31 measures the absolute position of the vehicle 1, that is, the position, posture, and speed of the vehicle 1 relative to a predetermined reference point, based on the measurement result of the positioning device 13 and an odometer using the detection result from the vehicle sensor 12. The map acquisition unit 32 acquires map information indicating the structure of the road on which the host vehicle 1 travels from the map database 14.

The detection integration section 33 integrates a plurality of detection results obtained by the object detection section 30 from a plurality of object detection sensors, respectively, and outputs one two-dimensional position, posture, size, speed, and the like for each object. Specifically, from the object behaviors obtained from the respective object detection sensors, the most reasonable object behavior with the smallest error is calculated in consideration of the error characteristics of the respective object detection sensors, and the like. Specifically, by using a known sensor fusion technique, detection results obtained by a plurality of sensors are comprehensively evaluated, resulting in more accurate detection results.

The object tracking unit 34 tracks the object detected by the object detecting unit 30. Specifically, based on the detection result integrated by the detection integrating unit 33, verification (correspondence) of the identity of the object at different times is performed based on the behavior of the object output at different times, and the behavior such as the speed of the object is predicted based on the correspondence.

The in-map position calculating unit 35 estimates the position and posture of the host vehicle 1 on the map from the absolute position of the host vehicle 1 obtained by the host vehicle position estimating unit 31 and the map information obtained by the map obtaining unit 32. The intra-map position calculation unit 35 determines the road on which the host vehicle 1 is traveling, and the lane 2 on which the host vehicle 1 is traveling and the adjacent lane 4 thereof on the road, and calculates the lateral position (vehicle width direction position, intra-lane lateral position) of the host vehicle 1 in the lane 2.

The vehicle control unit 36 drives the actuator 17 based on the result of prediction of the behavior of the object by the object tracking unit 34, the result of calculation of the position and posture of the host vehicle 1 by the intra-map position calculating unit 35, and the input of the occupant (for example, the driver) to control the travel of the host vehicle 1. The vehicle control unit 36 includes: a route setting unit 40, a route generating unit 41, a speed reduction time determining unit 42, and a control command value calculating unit 43.

The route setting unit 40 sets a target route (hereinafter simply referred to as "route") for a lane unit on which the host vehicle 1 should travel, based on the current position of the host vehicle 1 calculated by the intra-map position calculating unit 35 and the destination input from the occupant (or the navigation route set by the navigation device 15). The route is a statically set target route, and is set based on the shape of the lane of the high-precision map stored in the map database 14 and the shape of the lane boundary line detected by the object sensor 11. For example, the lane center of the road on which the vehicle travels when moving from the current position to the destination may be set as the route.

The route generation unit 41 determines whether or not the host vehicle 1 has performed driving behavior such as lane change, and sets a target route (hereinafter, simply referred to as "route") on which the host vehicle 1 should travel based on the determination result. The path is dynamically set according to the driving behavior of the host vehicle 1, and for example, when the host vehicle 1 is caused to make a lane change according to traffic conditions, the path generating unit 41 generates a movement path of the host vehicle 1 from a lane before the lane change to a lane after the lane change based on a vehicle model of the host vehicle 1. Conversely, when the host vehicle 1 is not caused to make a lane change, a route conforming to the route is generated. The path P generated by the path generating unit 41 may be dot matrix data as shown in the following equation (1).

P＝[P _L ，P _L+1 ，…，P _L+M ]… (1)

In addition, P of formula (1) _L+M To advance by M M from the current position]Is provided for the data of points on the path of (a). The route P is information indicating the shape of the route to be traced by the host vehicle 1, and does not include information on the vehicle speed. Points P of the lattice _L+i For example, the position (x, y), the posture (θ), and the curvature (κ) are used. The position (x, y) represents coordinates in a map coordinate system, and the posture (θ) represents a traveling direction (tangential direction) of a path at each point.

The speed reduction time determination unit 42 detects or estimates a vehicle speed reduction time T1, which is a time when the own vehicle 1 starts decelerating relative to the target stop position and the current vehicle speed v of the own vehicle 1 falls below a predetermined speed threshold VTH. First, the speed reduction timing determination unit 42 determines whether or not an object as a stop target is present in front of the host vehicle 1. The stop target includes, for example, an object to be stopped immediately before all the host vehicles 1, such as a preceding vehicle, a stop line, a pedestrian, and a crosswalk on the lane 2 on which the host vehicle 1 is traveling. When an object as a stop target is present in front of the host vehicle 1, the speed reduction time determination unit 42 sets the target stop position to a position immediately before the predetermined distance of the stop target.

Next, the speed reduction timing determination unit 42 determines whether or not the host vehicle has started decelerating relative to the target stop position. For example, when the following expression (2) is satisfied, the speed reduction time determination unit 42 may determine that the own vehicle starts decelerating relative to the target stop position.

L < v ² /(2a) … (2)

The expression (2) L is a distance from the current position of the host vehicle 1 to the target stop position, v is the current vehicle speed of the host vehicle 1, and a is a predetermined deceleration (set value). The speed reduction time determination unit 42 determines that the vehicle has started decelerating relative to the target stop position when the distance from the current position to the target stop position is shorter than the distance until the vehicle stops at the constant deceleration a.

When the above expression (2) is established, the speed reduction timing determination unit 42 sets the deceleration start flag Fd to "True", and then determines that deceleration is being performed with respect to the target stop position without performing the evaluation of (2) until the next deceleration start cancellation condition (a) or (B) is established.

(A) After it is determined that deceleration has started, the host vehicle has stopped to the target stop position.

(B) After it is determined that deceleration has started, the target stop position is changed or canceled. For example, the preceding vehicle as the stop target is advanced. Since the signal lamp on which the stop line as the stop target is set is changed from the stop display (red light) to the traveling display (green light), the target stop position is canceled.

When the deceleration start cancellation condition (a) or (B) is satisfied, the speed reduction timing determination section 42 cancels the determination indicating that the own vehicle 1 has started decelerating with respect to the target stop position, and sets the deceleration start flag Fd to "False".

Next, the speed reduction timing determination unit 42 determines whether the vehicle 1 is about to stop. For example, when the current vehicle speed V of the host vehicle 1 is lower than a predetermined speed threshold V _TH In the case of (2), it is determined that the host vehicle 1 is about to stop.

When it is determined that the vehicle 1 is about to stop after it is determined that the vehicle 1 has started decelerating relative to the target stop position, the speed reduction time determination unit 42 detects a speed reduction state of the vehicle 1. The speed reduction time determination unit 42 detects a time when the speed reduction state is first detected as a vehicle speed reduction time T1.

The speed reduction time determination unit 42 may estimate that the current vehicle speed v is lower than the current vehicle speed v of the vehicle 1 based on the current vehicle speed v and the decelerationSpeed threshold V _TH After determining that the own vehicle 1 has started decelerating relative to the target stop position, the vehicle speed V is lower than the speed threshold V _TH Is estimated as the vehicle speed reduction time T1.

That is, the "speed reduction state" is a state in which the host vehicle 1 starts decelerating relative to the target stop position, and the vehicle speed V is smaller than the speed threshold V _TH Is a state of (2). The "vehicle speed reduction time T1" is when the vehicle speed V is reduced to be less than the speed threshold V after the vehicle 1 starts decelerating relative to the target stop position _TH Is a time of day (c).

The speed reduction time determination unit 42 records the deviation of the own vehicle 1 from the path P in the lane width direction at the vehicle speed reduction time T1 as the lateral deviation Yoff. When the path P is generated along the lane center, the lateral deviation Yoff becomes the lateral deviation of the host vehicle 1 with respect to the lane center. Instead of the lane center, a lateral deviation from the lane boundary line can also be recorded. The speed-decrease-timing determination unit 42 sets the recorded-completion flag Fr indicating that the lateral deviation Yoff has been recorded to "True". The speed reduction timing determination section 42 can determine whether the speed reduction state is detected first based on whether the recorded completion flag Fr is "False" or "True".

On the other hand, when it is not determined that deceleration has started or when it is not determined that stopping is imminent, the speed reduction timing determination unit 42 does not detect the speed reduction state of the host vehicle 1. At this time, the recorded completion flag Fr is set to "False".

Next, the control command value calculation unit 43 calculates a control command value for moving the host vehicle 1 along the route P generated by the route generation unit 41 while maintaining the distance from the surrounding object. The control command value calculation unit 43 calculates a speed command value of the host vehicle 1 based on the distance to the target stop position, the relative speed to the stop target, and the relative acceleration. Then, based on the speed command value and the path P, the target travel locus X of the host vehicle 1 is calculated by calculating the target position, posture, speed, and curvature of the host vehicle at each time t+i×dt (i is an integer of 1 to N) of N steps from the current time t to t+n×dt seconds later.

The target travel track X is a lattice on a track indicating a state of the host vehicle 1 in the future for a certain period of time, and is represented by, for example, a lattice of the following formula (3).

X ＝ [X _t ，X _t+dt ，X _t+2dt …，X _t+N×dt ]… (3)

X _t+T The target state of the host vehicle after T seconds is expressed by the position (x, y), attitude (θ), velocity (v), and curvature (κ).

The control command value calculation unit 43 calculates the predicted trajectory Xp of the host vehicle 1. The predicted trajectory Xp is a trajectory for predicting the future vehicle state, and is a trajectory that is as close as possible to the target trajectory while avoiding the obstacle, with the current position of the host vehicle 1 as a base point. The components of the points of the predicted trajectory Xp are the same as the components of the points of the target travel trajectory X.

An example of a method of calculating the target travel locus X by the control command value calculation unit 43 will be described below. The control command value calculation unit 43 repeats n steps to obtain a point X based on the previous step _t+T-dt Calculating the point X of the target track at the time t+T _t+T To calculate the lattice of X _t ，X _t+dt ，X _t+2dt …，X _t+N×dt ]. Specifically, the point X from the previous step is calculated _t+T-dt The position and posture advanced along the path P by the displacement D only, and taken as a point X _t+T 。

The displacement D is obtained by the following equation (4).

D ＝ v _{t +T-dt} × dt … (4)

v _t+T-dt : point X of the target track of the previous step _t+T-dt Speed of (2)

dt: step time width

The control command value calculation unit 43 calculates the target locus point X based on the target locus point X _t+T The distance to the target stop position is calculated as a speed command value.

For example, the control command value calculation unit 43 may calculate the speed command value V that minimizes the evaluation function F of the following expression (5) by optimization calculation.

[ mathematics 1]

In formula (5), lr _i Is the distance to the target stop position relative to the stop target i, L _i Is the current distance between the stop target i and the host vehicle 1, V _i Is the speed of the stop target i, vr is the set vehicle speed, W _L Is the weight of the inter-vehicle distance, W _V Is a weight for setting the vehicle speed.

When the speed-decrease time determination unit 42 detects the speed-decrease state of the host vehicle 1 (that is, when it is determined that the host vehicle 1 is about to stop after it is determined that the host vehicle 1 has started decelerating relative to the target stop position), the control command value calculation unit 43 corrects the point X of the target travel locus X based on the lateral deviation Yoff of the vehicle speed-decrease time T1, as shown in the following formula (6) _t+T 。

[ math figure 2]

Xc of formula (6) _t+T Representing corrected point X _t+T θ represents a point X _t+T The posture (traveling direction, tangential direction) of the target travel locus X. That is, the control command value calculation unit 43 causes the point X of the target travel locus X to pass through the point X according to the lateral deviation Yoff _t+T Point X of target travel locus X is corrected by lane width direction position movement of (a) _t+T 。

Fig. 4A and 4B show the effect of the above correction. Fig. 4A is an explanatory diagram of an example of the target travel track in the case where the host vehicle 1 is not in the speed reduction state. In this case, the target trajectory point X is generated to entirely follow the path P. In the example of fig. 4A, it is generated along the lane center 2C. After avoiding the left-hand parked vehicle 4a, the predicted trajectory Xp is generated as the return lane center 2c.

If the vehicle 1 immediately ahead of the target stop position P1 performs a turning operation along the predicted trajectory Xp while traveling at an extremely low speed, the steering wheel may move greatly as described above, and may give the occupant a sense of discomfort.

Refer to fig. 4B. When the speed reduction state of the host vehicle 1 is detected near the target stop position P1, the target travel locus X is corrected to maintain the lateral deviation Yoff. Thus, the lateral deviation Yoff when avoiding the parked vehicle 4a is not eliminated and the vehicle is parked, so that the movement of the steering wheel can be suppressed.

Refer to fig. 3. The control command value calculation unit 43 uses the generated target travel locus X to perform vehicle control of the host vehicle 1. In the vehicle control, for example, steering and vehicle speed of the host vehicle 1 are controlled.

In the vehicle control, a control input (acceleration/deceleration command value dV _in Steering command value dK _in ) So that the predicted trajectory Xp of the host vehicle 1 of n×dt seconds approaches the target travel trajectory X while maintaining a distance from the avoidance target object around the host vehicle. The control may be implemented using a general model predictive control.

For example, when the control input U is input to the host vehicle 1 at discrete time t+t, the control command value calculation unit 43 calculates a point Xp corresponding to the predicted trajectory Xp of the host vehicle 1 _t+T Point X of track with target _t+T The control input U at time t+t is calculated so that the evaluation function defined by the difference between the difference and the proximity of the own vehicle 1 to the avoidance object becomes smaller.

When the speed reduction state of the host vehicle 1 is not detected, the evaluation function J1 at each time t+t is defined, for example, as shown in the following equation (7).

[ math 3]

Here, W is _O 、W _X 、W _U Is a weight matrix, and Xe is (X _t+T -Xp _t+T )。A _i，t+T Is a variable indicating the proximity of the own vehicle 1 to the avoidance object i. For example, the object i may be surrounded by the object iThe area of the region where the avoidance target region overlaps with the own vehicle 1, and the variable corresponding to the distance between the avoidance target i and the own vehicle 1.

The predicted position Xp of the first term of the evaluation function J1 in the own vehicle 1 _t+T The number of cases of approaching the avoidance object i increases. A is that _i，t+T Is the state quantity Xp _t+T Is a function of the state quantity Xp _t+T Is the current state quantity Xp _t And a function of the control input U. Calculation of A by optimization calculation _i，t+T Minimized control input U.

In addition, the second term of J1 is the predicted state Xp of the own vehicle 1 _t+T With the target travel track X _t+T A difference value (コ test). The third term is the value of the absolute value of U. By using these as the total evaluation function, it is possible to calculate a control input in which avoidance of the object (first term), tracking of the target trajectory (second term), and stabilization of the control input (third term) coexist.

Here, when approaching the avoidance object (the parked vehicle 4 b) on the side of fig. 4C, a is set to be a with respect to the avoidance object _i，t+T And (3) increasing. To reduce A _i，t+T As indicated by reference numeral 6, it is necessary to make the predicted position Xp _t+T Offset to the left, thus steering command value dK _in And (3) increasing. At this time, if the host vehicle 1 is traveling at an extremely low speed before the target stop position P1, it is necessary to greatly steer in order to move leftward. Therefore, the steering command value dK _in A large value may give a sense of discomfort to the occupant.

In the present invention, when the speed reduction state of the vehicle 1 is detected near the target stop position P1, the control input U is calculated by an optimization calculation that minimizes the evaluation function J2 of the following equation (8).

[ mathematics 4]

Here, v _i 、v _t+T Is the speed of the own vehicle 1 while avoiding the object i.

In addition, A' _i，t+T The determination value of the proximity degree of the avoidance object i calculated by the host vehicle 1 with respect to the control input in the period preceding the calculation time t+t (that is, the proximity degree in the case where the control input U at the time preceding the time t+t is input to the host vehicle 1). Therefore, there is no change in the control input U. That is, the partial derivative of U is 0.

Therefore, the optimization calculation for A 'is not performed' _I，t+T An adjustment of 0. On the other hand, due to the proximity A' _I，t+T Multiplied by the relative velocity (vi-v _t+T ) Therefore, when approaching the avoidance object i, an adjustment is performed to match the vehicle speed with the avoidance object i. As a result, as shown in fig. 4C, the acceleration/deceleration command value dV at which the position P2 immediately before the object 4b is stopped is calculated _in 。

The control command value calculation unit 43 calculates a control input U that minimizes the evaluation functions J1 and J2. The control command value calculation unit 43 drives the actuator 17 based on the calculated control input U, and controls the speed and steering angle of the vehicle 1.

(action)

Fig. 5 is a flowchart showing an example of the vehicle control method according to the present embodiment.

In step S1, the controller 16 detects objects around the vehicle 1, a stop line, and a self position. In step S2, the speed reduction time determination unit 42 executes a speed reduction state detection process.

Fig. 6 is a flowchart of a first example of the speed reduction state detection process. In step S30, the speed reduction timing determination unit 42 determines whether or not the deceleration start flag Fd is "True". In the case where the deceleration start flag Fd is not "True" (S30: no), the process advances to step S31. In the case where the deceleration start flag Fd is "True" (yes in S30), the process advances to step S36.

In step S36, the speed reduction timing determination unit 42 determines whether or not the deceleration start cancellation condition is satisfied. When the deceleration start cancellation condition is not satisfied (S33: no), the process advances to step S33. When the deceleration start cancellation condition is satisfied (yes in S36), the process proceeds to step S37.

In step S37, the speed reduction timing determination unit 42 sets the deceleration start flag Fd to "False". Then, the process advances to step S31.

In step S31, the speed reduction timing determination unit 42 determines whether or not the own vehicle has started decelerating relative to the target stop position. When deceleration is started (yes in S31), the process proceeds to step S32. If deceleration has not started (no in S31), the process proceeds to step S35. In step S35, the speed reduction time determination unit 42 determines that the speed reduction state of the vehicle 1 is not detected. Then, the speed reduction state detection process ends.

In step S32, the speed reduction timing determination unit 42 sets the deceleration start flag Fd to "True".

Then, the process advances to step S33.

In step S33, the speed reduction timing determination unit 42 determines whether or not the vehicle 1 is about to stop. If the vehicle 1 is not about to stop (no in S33), the process proceeds to step S35, and it is determined that the speed reduction state of the vehicle 1 is not detected, and the speed reduction state detection process ends.

When the vehicle 1 is to be stopped (yes in S33), the process proceeds to step S34. The speed reduction time determination unit 42 determines that the speed reduction state of the host vehicle 1 is detected. Then, the speed reduction state detection process ends.

Refer to fig. 5. In the case where the speed decrease state is detected (S3: yes), the process proceeds to step S11. If the speed reduction state is not detected (no in S3), the process proceeds to step S4. The speed reduction timing determination unit 42 sets the recorded completion flag Fr to "False".

In step S5, the control command value calculation unit 43 initializes the variable i to "1". In step S6, the control command value calculation unit 43 calculates the point X of the target travel locus X at time t+i×dt _t+i×dt Is a position of (c). In step S7, the control command value calculation unit 43 calculates the target travel locus X point X _t+i×dt Is set, the speed command value of (a). In step S8, the control command value calculation unit 43 increases the value of the variable i by 1. In step S9, the control instruction valueThe arithmetic unit 43 determines whether the variable i is greater than N. If the variable i is not greater than N (no in S9), the process returns to step S6. If the variable i is greater than N (yes in S9), the process advances to step S10.

In step S10, the control command value calculation unit 43 calculates the control input U by reducing the optimization calculation of the evaluation function J1 of the above equation (7). Then, the process advances to step S21.

On the other hand, in step S11, the speed-down timing determination section 42 determines whether or not the speed-down state is detected first (i.e., whether or not the recorded completion flag Fr is "False"). If the speed reduction state is detected initially (yes in S11), the process proceeds to step S12. If the speed decrease state has been detected (no in S11), the process proceeds to step S14.

In step S12, the speed reduction timing determination unit 42 sets the recorded completion flag Fr to "True". In step S13, the speed reduction timing determination unit 42 records the lateral deviation Yoff. The processing of steps S14 to S16 is the same as the processing of steps S5 to S7.

In step S17, the control command value calculation unit 43 corrects the point X of the target travel locus X based on the lateral deviation Yoff _t+T 。

In step S18, the control command value calculation unit 43 increases the value of the variable i by 1. In step S19, the control command value calculation unit 43 determines whether the variable i is greater than N. If the variable i is not greater than N (no in S19), the process returns to step S15. If the variable i is greater than N (yes in S19), the process advances to step S20. In step S20, the control command value calculation unit 43 calculates the control input U by reducing the optimization calculation of the evaluation function J2 of the above equation (8). Then, the process advances to step S21.

In step S21, the control command value calculation unit 43 controls the host vehicle 1 with the control input U. In step S22, it is determined whether the ignition key has become off. If the ignition key is not turned off (no in S22), the process returns to step S1. When the ignition key is turned off (yes in S22), the process ends.

(modification)

(1) In the above embodiment, when either the deceleration start cancellation condition (a) "the own vehicle has stopped to the target stop position" or (B) "the target stop position is changed or cancelled" is established, the speed reduction timing determination section 42 cancels the determination that the own vehicle 1 starts decelerating relative to the target stop position. Instead, as shown in the flowchart of fig. 7, the determination of the deceleration start cancellation condition (B) may be omitted.

In step S40, the speed reduction timing determination unit 42 determines whether or not the vehicle 1 is in a stopped state. When the host vehicle 1 is in a stopped state (yes in S40), the process proceeds to step S41. If the vehicle 1 is not in the stopped state (no in S40), the process proceeds to step S42. In step S41, the speed reduction timing determination unit 42 sets the deceleration start flag Fd to "False".

In step S42, the speed reduction timing determination unit 42 determines whether the deceleration start flag Fd is "True". If the deceleration start flag Fd is "True" (yes in S42), the process proceeds to step S45. If deceleration start flag Fd is not "True" (no in S42), the process proceeds to step S43. The processing of steps S43 to S47 is the same as the processing of steps S31 to S35 of fig. 6.

(2) The determination of the deceleration start cancellation conditions (a) and (B) described above is a determination to detect "deceleration no longer required for stopping", and may be replaced by a determination as to whether or not the following expression (9) is satisfied.

L>v ² /(2a)+L _TH …(9)

L _TH : determination of tolerance

That is, when it is determined that the situation changes after the vehicle 1 starts decelerating relative to the target stop position, the margin to the target stop position may be set to L _TH In this way, the determination that the own vehicle 1 has started decelerating relative to the target stop position is canceled.

(3) Further, the speed reduction state of the host vehicle 1 may be detected by combining the condition of the above formula (9) and the condition of the above formula (1). Fig. 8 is a flowchart of a third example of the speed reduction state detection process.

In step S50, the speed reduction timing determination unit 42 determines whether or not the vehicle 1 is decelerating. The speed reduction time determination unit 42 determines that the vehicle 1 is decelerating when the following expression (10) is satisfied.

L<v ² /(2a)+L _TH …(10)

When the vehicle 1 is decelerating (yes in S50), the process proceeds to step S51. If the deceleration is not in progress (no in S50), the process proceeds to step S53.

In step S51, the speed reduction timing determination unit 42 determines whether or not the vehicle 1 is about to stop. When the vehicle 1 is about to stop (yes in S51), the process proceeds to step S52. If the vehicle 1 is not about to stop (no in S51), the process proceeds to step S53. In step S52, the speed reduction time determination unit 42 determines that the speed reduction state of the host vehicle 1 is detected. In step S53, the speed reduction time determination unit 42 determines that the speed reduction state of the host vehicle 1 is not detected. In the determination of step S50 of fig. 8, the determination condition of whether or not the deceleration is in progress relaxes the margin L _TH But is the same as the above embodiment if it is combined with the determination of whether or not step S51 is about to stop.

(4) Further, if the threshold value that determines whether the own vehicle 1 is about to stop is taken into consideration as the vehicle speed V _TH In step S50 of fig. 8, the condition L may be satisfied according to whether or not<V _TH ² /(2a)+L _TH To determine whether the own vehicle 1 is decelerating. In this case, since the vehicle speed V of the own vehicle is indirectly considered to be at the threshold value V _TH Hereinafter, the step S51 of determining whether or not to stop is therefore omitted.

(effects of the embodiment)

(1) The controller 16 performs the following processing: the method includes a vehicle speed determination process of determining whether or not the vehicle speed of the own vehicle has fallen below a predetermined speed threshold value, a lateral deviation detection process of detecting a lateral deviation of the own vehicle with respect to the center of the lane or the lane boundary line, a target track generation process of generating a first target travel track of the own vehicle so as to suppress a change in lateral deviation after a vehicle speed reduction time, which is a time point when the vehicle speed has fallen below the speed threshold value, a avoidance object detection process of detecting a avoidance object to be avoided by the own vehicle, and a avoidance process of avoiding the avoidance object by adjusting the deceleration of the own vehicle while traveling along the first target travel track after the vehicle speed reduction time point.

This can suppress the change in rudder angle that accompanies avoidance of an object when the speed of the host vehicle is low. This can suppress the uncomfortable feeling of the occupant caused by the large movement of the steering wheel.

(2) The controller 16 may execute a process of setting a target stop position in front of the host vehicle and a process of determining whether or not the host vehicle starts decelerating with respect to the target stop position, and execute a target trajectory generation process and a avoidance process when it is determined that the host vehicle starts decelerating with respect to the target stop position and it is determined that the vehicle speed is reduced to be less than the speed threshold. This can suppress the rudder angle change only when stopping at the target stop position.

(3) The controller 16 does not execute the target trajectory generation process and the avoidance process when it determines that the host vehicle has stopped to the target stop position or the target stop position has been changed or canceled after it determines that the host vehicle has started decelerating from the target stop position. This can prevent unnecessary rudder angle changes from being suppressed.

(4) The controller 16 may execute a process of calculating a required distance that can be stopped at a predetermined deceleration to the target stop position based on the current vehicle speed of the host vehicle, determine that the host vehicle starts decelerating with respect to the target stop position when the distance from the host vehicle to the target stop position is smaller than a distance threshold set based on the required distance, and execute the target trajectory generation process and the avoidance process when it is determined that the host vehicle starts decelerating with respect to the target stop position and the vehicle speed is reduced to be smaller than the speed threshold. This makes it possible to determine whether or not the host vehicle is decelerating to the target stop position.

(5) The controller may generate the second target travel locus based on the lane shape, and generate the first target travel locus by moving the lane width direction position of the second target travel locus in accordance with the lateral deviation detected at the time of the vehicle speed reduction. Thus, the target travel locus maintaining the lateral deviation can be calculated.

(6) The controller may execute processing for calculating the control input so as to reduce an evaluation function corresponding to a difference between the predicted position of the host vehicle and the first target travel locus when the control input of the acceleration/deceleration and the steering angle is input to the host vehicle and a degree of approach of the host vehicle to the avoidance target object, wherein the evaluation function to be evaluated when the control input is calculated at the first time includes a term obtained by multiplying the degree of approach of the control input calculated at the second time preceding the first time to the host vehicle by the relative speed of the avoidance target object to the host vehicle. Thus, the avoidance target can be avoided by adjusting the deceleration.

Symbol description:

1: own vehicle, 2: lane, 2c: lane center, 3: preceding vehicle, 4a, 4b: parking vehicle, P1: target stop position, X: target travel track, xp: predicted trajectory, yoff: lateral deviation of

Claims (7)

1. A vehicle control method characterized by causing a controller to execute:

a vehicle speed determination process of determining whether or not the vehicle speed of the host vehicle has fallen below a predetermined speed threshold value;

a lateral deviation detection process of detecting a lateral deviation of the host vehicle with respect to a lane center or a lane boundary line;

a target trajectory generation process of generating a first target travel trajectory of the host vehicle so as to suppress a change in the lateral deviation at or after a vehicle speed reduction time, which is a time when the vehicle speed is reduced to be less than the speed threshold, when it is determined that the vehicle speed is reduced to be less than the speed threshold;

an avoidance object detection process of detecting an avoidance object to be avoided by the host vehicle;

and a avoidance process of avoiding the avoidance target object by adjusting deceleration of the host vehicle while the host vehicle is traveling along the first target travel locus after the vehicle speed reduction time.

2. The vehicle control method according to claim 1, characterized in that,

the controller performs the following processing:

a process of setting a target stop position in front of the host vehicle;

determining whether the own vehicle starts a process of decelerating with respect to the target stop position,

the target trajectory generation process and the avoidance process are executed when it is determined that the own vehicle starts decelerating with respect to the target stop position and it is determined that the vehicle speed decreases to be less than the speed threshold.

3. The vehicle control method according to claim 2, characterized in that,

the controller does not execute the target trajectory generation process and the avoidance process when the vehicle stops at the target stop position or the target stop position is changed or canceled after determining that the vehicle starts decelerating relative to the target stop position.

4. The vehicle control method according to claim 2 or 3, characterized in that,

the controller performs a process of calculating a required distance that can be stopped at a prescribed deceleration to the target stop position based on the current vehicle speed of the host vehicle,

when the distance from the host vehicle to the target stop position is smaller than a distance threshold set according to the required distance, it is determined that the host vehicle starts decelerating with respect to the target stop position,

the controller executes the target trajectory generation process and the avoidance process when it is determined that the own vehicle starts decelerating with respect to the target stop position and it is determined that the vehicle speed decreases to be smaller than the speed threshold.

5. The vehicle control method according to any one of claims 1 to 4, characterized in that,

the controller generates a second target travel track based on a lane shape, and generates the first target travel track by moving a lane width direction position of the second target travel track in accordance with the lateral deviation detected at the vehicle speed reduction timing.

6. The vehicle control method according to any one of claims 1 to 5, characterized in that,

the controller executes processing for calculating a control input for inputting an acceleration/deceleration and a steering angle to the host vehicle so as to reduce an evaluation function corresponding to a difference between a predicted position of the host vehicle and the first target travel locus and a degree of proximity of the host vehicle to the avoidance object,

the evaluation function evaluated at the time of computing the control input at a first timing includes: a term obtained by multiplying the proximity degree at the time of the control input calculated at a second time before the first time by a relative speed of the avoidance object with respect to the own vehicle is input to the own vehicle.

7. A vehicle control device is provided with a controller that executes the following processing,

a vehicle speed determination process of determining whether or not the vehicle speed of the host vehicle has fallen below a predetermined speed threshold value;

a lateral deviation detection process of detecting a lateral deviation of the host vehicle with respect to a lane center or a lane boundary line;

a target trajectory generation process of generating a first target travel trajectory of the host vehicle so as to suppress a change in the lateral deviation at or after a vehicle speed reduction time, which is a time when the vehicle speed is reduced to be less than the speed threshold, when it is determined that the vehicle speed is reduced to be less than the speed threshold;

an avoidance object detection process of detecting an avoidance object to be avoided by the host vehicle;

and a avoidance process of avoiding the avoidance target object by adjusting deceleration of the host vehicle while the host vehicle is traveling along the first target travel locus after the vehicle speed reduction time.